Mattoo et al studied the depth of penetration of lead shot. They correlated the depth to the ratio of energy to area of presentation for the missile. The authors are from the Forensic Science Laboratory in Bombay (Mumbai). India.


Projectile: lead shot



(1) depth of penetration in cm

(2) energy to area of presentation in meters • kg per square cm


cm penetration =

= (2 * (E-to-a ratio)) - 2.5


If this is rearranged:


estimated E-to-a ratio in m•kg per square cm =

= (0.5 * (cm of penetration)) + 1.25



• The E/a ratio threshold for human skin penetration is 1.25 m•kg per square cm.

• The threshold velocity for skin penetration by a steel sphere is 125-170 feet per second (Office of Surgeon General, Department of the Army. Wound Ballistics. 1962).

• The conversion factor for m•kg per square cm to ft•lb per square inch is 46.54 by my calculation.


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